some questions:
• how far away from the WLS transmitter in Tinley Park was the interference received on the radio receiver? if the station isn’t a local grade signal, there are plenty of electronic devices that can easily interfere with AM signals, even local strong signals. (note that in recent years a number of people have said the WLS 890 signal is weaker due to the surrounding area of the transmitting getting built up and lowering ground conductivity)

• email or call the engineer at the station and ask if they’re aware of any interference issues?

• there is something called PLC that the utilities, primarily ComEd use, that sends coded signals over the power lines - these power lines could have been leaking interference...

remote possibility someone is trying to jam the WLS signal, but why? nothing really worth jamming on the big 89 now, lol...